This invention is directed generally to the field of hydraulic control and more specifically to devices for hydraulically positioning a workpiece in response to electrical control signals.
Prior hydraulic systems have been devised for crudely positioning a workpiece such as a hydraulically operated piston. However, when such systems have been modified to exert more precise control over the distance to be moved or the rate of movement of a workpiece, it has been found necessary to include a complex assortment of plumbing hardware in the basic hydraulic system. For example, flow control valves, pressure regulators, check valves, analog servo valves, etc., have been conventionally used in analog fluid control systems.
In addition to requiring a complex array of plumbing hardware, prior hydraulic systems have typically included an equally complex electronic control system, thereby rendering the over-all system very expensive. Moreover, the precision and reliability of such prior systems vary with variations in the temperature and pressure of the fluid, as well as the extent of air entrapment in the fluid.